Hi
i m looking a circuit for colpitts oscilator working in bread board


thank you

George

 

What frequency oscillation?

 

straight from Horowitz (Art of Electronics)

 

Practical and inexpensive, has many uses.
This Colpitts variable frequency generator outputs 2-10 MHz sine wave.
A simple low or high pass filter will bring out the harmonics.
Adding a simple wide band amplifier stage makes it even more practical.

 

Many high frequency circuits will not work on a breadboard because of the capacitance between the rows of contacts and the messy wires all over the place.

 

One caution is that if an FET or MOSFET is used for the active device, you really MUST have that source to common resistor, and a higher value is better. The reason is that with excessive gain there will be clipping and lots of harmonics in the signal. So the source resistor provides some negative feedback to hold the amplitude i check.
So it is better to use a bipolar (NPN) transistor, still with an emitter resistor, for a COLPITS oscillator. You can totally ignore what Mr DEMAW claims. His priority was always fast oscillator starting, although he seldom mentioned that.

 

Using an NPN transistor for a Colpitts oscillator, in a tutorial shows some math, operating point and the output simulated
Analog Tutorial Lesson 10: Designing High Frequency BJT Colpitts Oscillators - Emagtech Wiki